With the increased demand for high-output semiconductor light emitting devices (LEDs), modules comprising an array of light emitting elements are often used. The individual light emitting elements may be “mid-power”, consuming less than a half watt, and dozens may be contained in the array, providing relatively high light output intensity.
To produce a desired color, such as white light, light of different wavelengths are combined. In some embodiments, the array of light emitting elements may include sets of light emitting elements of different color, such as red, blue, and green/yellow. The intensity of the light output of each color will define the color of the composite light output from the array.
In other embodiments, the array of light emitting elements may all emit light of the same wavelength, and wavelength conversion material may be used to convert at least a portion of the light emitted by the light emitting elements to different wavelengths, such that the light output is a combination of the originally emitted light and the wavelength converted light. This wavelength conversion material is commonly contained in the encapsulant that covers the array.
“Chip-on-Board” (COB) is an array architecture that is commonly used because of its flexibility and low cost. A COB may comprise an array of light emitting elements arranged on a substrate and covered by an encapsulant within a ring or dam surrounding the light emitting elements. The encapsulant may be a silicone compound that is poured into the dam then cured, or it may be a preformed element, such as a silicone sheet or a ceramic that is contained within the ring. Commonly, the encapsulant includes a wavelength conversion material that converts the light emitted by the light emitting elements to one or more other wavelength.